Fuel control systems for supplying fuel to primary and main burners in a gas turbine engine

ABSTRACT

Fuel control systems for supplying fuel to the primary and main burners in gas turbine engines of the fan-type in which means are provided for controlling the primary fuel supply in accordance with the engine compressor pressures. A variable operator control valve is utilized for supplying fuel to the main burner and means are included to maintain the flow rate to the main burners as a function of that of the primary burners.

m 1111111001 @tntes 1%116111 1151 3,663,627 Lawrence 61 nl, 51 Feb. 22,11972 [54] FUEL CUNTRUL SYfi'lllEMS IFQTR 2,988,883 6/1961 Corbett..60/39.28 P H E pg IM AND 3,000,436 9/1961 Lawrence... ..60/2433,067,576 12/1962 Campbe1l..... ..60/241 MAIN BKJRNERS EN A GAS TIURBHNE3,095,702 7/1963 Brown 60/3928 ENGHNE 3,234,730 2/1966 Deitweiler60/3928 [72] Inventors: Owen Napier Lawrence, -Boxford, near 32439554/1966 Frank "60/243 3,280,560 10/1966 Marchant ....60/226 Newbury,Eugene 11111110101 Wnrne, Sollhull, 3 338 051 8/1967 Ch, b wlzz 7 bothofEngland am Cl 1n ..1 a

[73] Assignee: Joseph Lucas (lndustlries) Limlted, Birmingham, England IPrimary Examiner-Laurence M. Goodridge [22] Flled' W69 Attorney-Holman &Stern [21 Appl. No.: 852,386

Related US. Application Data [63 1 Continuation-impart Of Ser. No.624,016, Mar. 17, [571 1967, abandoned Fuel control systems forsupplying fuel to the primary and main burners in gas turbine engines ofthe fan-type in which U68. means are provided for controlling theprimary fuel upply in [51] llnt. Cl. ..F02c 9/04 accordance with theengine compressor pressures, A variable [58] Field 01 Search ..60/39.28,241 243, 226, 261 operator control valve is utilized for supplying fuelto the main burner and means are included to maintain the flow rate tothe [56] References Cited main burners as a function of that of theprimary burners.

UNITED STATES PATENTS 2,636,553 4/ 1953 Ballantine ..60/243 4 Claims, 4Drawing Figures MIEIIEBFEBZZ I972 SHEET 2 OF 4 I anew bJn m1:

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FUEL CONTROL SYSTEMS FOR SUlPlP'LYING FUEL TO PRIMARY AND MAIN BURNIERSIN A GAS TURBINE ENGINE BACKGROUND OF Til-IE INVENTION This applicationis a continuation-in-part of our copending application Ser. No. 624,016filed Mar. 17, 1967 and entitled FUEL CONTROL SYSTEMS FOR GAS TURBINEEN- GINES, now abandoned.

The present invention relates to fuel control systems for use in gasturbine engines and more particularly of the type for supplying fuel tosets of primary and main burners.

SUMMARY OF THE INVENTION The primary object of the invention is toprovide fuel control systems for supplying fuel to the primary and mainburners in a gas turbine engine of the fan type in which there is meansfor controlling the fuel supply to the primary burners in accordancewith changes in a predetermined parameter, a variable operator controlvalve to control the fuel supply to the main burners, and means tomaintain the flow rate to the main burners as a function of the flowrate to the primary burners.

Further important advantages of the invention will become more readilyapparent to persons skilled in the art from the following detailedspecification and annexed drawings and in which drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a diagrammatic view of a gasturbine engine of the fan type equipped with an auxiliary fuel controlsystem embodying the present invention,

FIG. 2 is a diagrammatic view of the fuel system associated with theapparatus illustrated in FIG. 1,

FIG. 3 is a diagrammatic view of a gas turbine engine of the fan typeprovided with an alternative fuel control system, and

FIG. 4 is a diagrammatic view of the fuel system utilized in theapparatus in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION While the two embodimentsaccomplish the same results, in the system illustrated in FIGS. I and 2the principle of the control is that the pressure of the fuel flowing tothe primary burners is controlled in accordance with the fan inlet andthe rise in the outlet pressure. In other words, the pressures existingin the main and primary burner passages are balanced so that the flow tothe main burners is maintained at a fixed proportion to the flow to theprimary burners. The system shown in FIGS. 3 and 4 relies upon flowrates and pressure drops rather than upon the actual pressures existingin the passages and thereby relies upon the flows to the main andprimary burners respectively.

As above mentioned, the invention is for use in gas turbine engines ofthe fan type in which at the upstream end of the engine there isprovided a fan I which is driven by the engine and which delivers airinto a duct 2. The engine, as illustrated, in cludes a compressor 3 andtwo turbines 4 and 5. One of the turbines drives the compressor 3 andthe other turbine the fan I. A combustion apparatus 6 is located betweenthe compressor and turbine stages of the engine.

Auxiliary fuel systems are used to provide fuel to the duct 2 under thecontrol of an operator, which, in the case of aircraft, is the pilot, inorder that combustion can be affected within the duct 2 for providingadditional thrust. More particularly, the invention is for use in anengine of this character in which the direction of thrust can be variedand at the same time the efiective area of the exhaust outlet alsovaried, with additional thrust being required when the exhaust outlet isdirected to provide a component of lift to the aircraft.

As clearly illustrated in FIG. I, primary and main burners Ill and IIrespectively are located in the duct 2 and this duct is generallyreferred to as a plenum chamber. Fuel is also supplied by the auxiliarysystem to burners l2 operably associated with igniters. As is customaryin gas turbine engines, the primary and main burners are required tooperate simultaneously so that large flow changes can be accommodatedwithout impairing the atomization efficiency.

The system can be made operative by the pilot of the aircraft by meansof a link 113 which executes the functions of opening a valve 115,admitting air under pressure obtained from the compressors to a turbinet7 of a pump 16, opening a valve 119 in a supply line from a fuelreservoir (not illustrated) in order that the fuel can reach the pumpI8.

A second pilot lever 14 can be actuated when the system is operative forcontrolling a valve 16in series with the valve 115 which is coupled to adifferent mechanism which forms no part of this invention. The movementof the lever 14 also controls a variable multiple valve 20 provided withthree lands for controlling the fuel flow from the pump I8 through aservooperated throttle valve 21 to the pipes leading to the primary,main and igniter burners I0, I11 and I2 respectively.

The fuel flow to the primary burners is controlled as a function of thepressure rise across the engine fan although other parameters could beutilized and the manner in which this is accomplished will be later morefully described. The pilot sets the lever 14 for the fuel supply whichis necessary to produce the required performance but the throttle valve21 regulates the fuel which actually reaches the burners.

In order to control the flow to the primary burners, there is provided abody 22 within which a. flexible diaphragm 25 serves to define twochambers 23 and 24. To one of the chambers, the pressure of air upstreamof the fan is admitted and the pressure of the air downstream of the fanis admitted to the other chamber. An evacuated capsule 26 is positionedwithin the chamber 23 and between the capsule 26 and a rod 27 connectedto the center of the diaphragm 25 is located one end of a lever 28pivotally mounted in the wall of the body 22 as indicated at 29. Thebody 22 is further provided with a chamber 30 into which the oppositeend of the lever 28 extends and such end of the lever carries ahalf-ball 311 which is engageable with a seat 32 in the wall of the body2-2 by virtue of the action of spring 33.

The seat 32 constitutes the end of a passage or conduit 34 communicatingwith one end of a servo cylinder 35 of the throttle valve 21. A piston36 loaded by a spring 37 is mounted within the cylinder and is biasedtowards the end at which the passage 34 enters the cylinder. The piston36 is provided with a valve head 38 and the position of the valve headcontrols the fuel flow rate through a pipe or conduit 39 leading fromthe pump 14 to the multiple valve 20. The body 22 is further formed witha cylinder 40 in which is mounted a piston 411 pro vided with anextension adapted to engage the lever 26 at a location between the pivot29 and the half ball 31. The opposite end of the cylinder 40 is incommunication by means of a passage or conduit 42 with the primaryburners l0 and the juncture between the passage 42 and the pipe to theprimary burners is downstream of a fixed restrictor 43 located in suchpipe. A pressure is maintained at the burners downstream of therestrictor 43 which is dependent upon the pressure rise across the fanin the engine and the half ball 31 controls the flow through thethrottle valve 211 in accordance with this valve.

It is necessary not only to maintain a pressure in the primary burners110 which is in accordance with the fan pressure rise but to translatethis such that the flow to the primary burners is in the samerelationship. In order to achieve such ends, the pipe to the primaryburners 110 includes a pressure responsive spring loaded valve 44 whichcontrols the flow through a variable orifice of known type in accordancewith the applied pressure. As illustrated in FIG. 2, the valve 44 may bereplaced by a known type of alternative burner illustrated at 45 andwhich is arranged to produce the same effect.

Since it is necessary that the fuel flow rate to the main burner is afunction of the flow rate to the primary burners Ill, this is realizedby ensuring that the pressure downstream of the restrictor 43 in thepipe to the primary burners is also that in the pipe to the main burners11. For maintaining this pressure, there is provided a device 46 havingtwo chambers 47 and 48 divided by a flexible diaphragm 49. into thechamber 47 at one side of the diaphragm 49, fuel at the pressureexisting in the passage 42 downstream of the restrictor 43 is ad mitted.The other chamber 48 is in the fuel flow path between the multiple valve20 and the main burners l1 and the pressures are maintained equai bymovement of the diaphragm for determining the opening of an outletorifice communicating with the pipe leading to the burners 11. Since thepressure drop across the fixed restrictor 43 is maintained the same asthat across the orifice which is varied by the position of the diaphragm49, the flow in the pipe to the main burners 11 will be a predeterminedfunction of that in the pipe to the primary burners 10. The device 46incorporates a pressure relief valve 50 between the chambers 47 and 48for preventing damage to the diaphragm under the influence of a suddenchange in pressure. The pipe leading to the main burners 1 1 is alsoequipped with a nonreturn valve 51 for maintaining pressure in thechamber 48 as well as preventing damage to the diaphragm in the eventthe multiple valve 20 is moved rapidly to cut off flow to the mainburners. The valve 51 will also prevent back pressure in the mainburners, reaching the chamber 48.

As previously mentioned, the principle of this particular control isthat the pressure of the fuel flowing to the primary burners iscontrolled in accordance with the fan inlet and outlet pressure rise.This pressure control is achieved through the passage 42 from thepassage to the primary burners 10, which, together with the diaphragm25, controls the position of the half ball 31 which in turn controls theoperation of the throttle valve 21. The pressure existing in the passageto the primary burners 10 is balanced in the device 46 against thepressure in the passage to the main burners 11 and this balance controlsthe flow to the main burners by the control member carried by theflexible diaphragm 49.

In the system illustrated in FIGS. 3 and 4, the principle is that thepressures existing in the main and primary burner passages are balancedso that the flow to the main burners is maintained at a fixed proportionto that to the primary bur ners. in this embodiment, parts correspondingto those illustrated in FIGS. 1 and 2 will bear similar referencenumerals except they are primed. It should be mentioned that the lever14 operates the variable multiple valve 21 which is positioned in theseparate pipes to the burners 10, 11' and 12'.

The fuel supply to the burners 10 through its associated pipe or conduitis via a device denoted generally 52. The device 52 includes a cylinder53 in which is mounted a spring loaded piston 54 having a sleevelikeextension 54a provided with apertures 54b. The wall of the cylinder 53includes an inwardly extending annulus which coacts with the extension54a for controlling the fuel flow from a passage 55 from the pump 18'through the throttle valve 21' to a chamber 56 and thence through a pipeor conduit 61 to the pipe to the primary burners 10' via the multiplevalve The piston 54 is connected to a tension spring 57 and the oppositeend of the spring 57 is attached to a lever 58 which carries a half ball59 at one end thereof. The half-ball 59 controls the entry of fuel intothe chamber 56 from a chamber provided at the end of a cylinder 53remote from the spring 57. This chamber receives fuel through an orificein the piston 54.

The body of the device 52 is formed with a seat 60 with which thehalf-ball 59 cooperates. A further passage 62 leads to a chamber 63 inwhich is disposed an adjustably springloaded piston 64 which actsagainst the end of a lever 65 which is pivoted at 66 within the device52. The other end of the lever 65 carries a half-ball 67. The half-ball67 is adapted to cooperate with a seat 68 which serves as thetermination of a passage 69 which leads to the throttle valve 21. Theopposite end of the piston 64 is subject to the pressure of the fuel inthe passage 55 upstream of the sleevelike extension 54a of the piston54. This arrangement is capable of maintaining at a constant value thepressure drop across a restriction defined by the slee elike extension54a by varying the throttle valve 21'.

Furthermore, the lever 58 at its end remote from the halfball 59 extendsinto a chamber 70 and is pivoted within the device 52 as at 71 which isin the nature of a wall dividing the chambers 56 and 70. The lever 58engages a capsule or bellows 72 to which air at the pressure upstream ofthe engine fan 1' is admitted and air at the pressure downstream of thefan is introduced into the chamber 70. The pressure difference actingupon the lever 58 is balanced by the spring 57 so that the position ofthe piston and hence the flow to the primary burners is proportional tothe pressure difference existing in the chamber 70 and the capsule 72.

The main burner 11' is fed via a pipe or conduit 73 from the throttlevalve 21' and the pipe 73 incorporates a unit 74 constituted by aspring-loaded member 75 arranged so as to produce within the pipe apressure drop equal to the constant pressure drop developed by thedevice 52. Any change in the pressure drop at the device 52 as aconsequence of a change in the position of the throttle valve 21' willeifect a similar change at the unit 74. The pressure at the main burners11' will always be a function of that at the primary burners.

It will be appreciated that the burners per se define restrictors in thepipes and these also will be in fixed relationship to one another. Theflow rates to the burners will as a result also be in the samerelationship as the pressure drops in the respective flow paths.

It will be noted that the pipe leading to the ignition burners 12 isonly controlled by the throttle valve 21' and the multiple valve 20'although it is arranged to cut off when relatively high flow through thevalve 20' is occurring to the other burners.

By virtue of the present invention there is provided a device forcontrolling the fuel flow to the primary burners 10 which is responsiveto pressures received from the engine fan 1' for providing a bleed whichin turn controls the throttle valve 21' via the half-ball 67. Thepressure drop developed by the device 52 in the primary burner passageis matched by an equal pressure drop in the main burner passage to themain burners 11 by means of the unit 74. While the unit 74 is extremelysimple in structural detail, its design is such that its characteristicperformance is capable of producing the same pressure drop as thatdeveloped by the device 52. Hence, this particular embodiment reliesupon the flows to the main and primary burners respectively.

It is to be understood that the various components constituting thesystems may be replaced by other components designed to performequivalent functions. Moreover, the in vention is also applicable toengines of other types such as the bypass type engine which is similarto the fan type except the air entering the duct is received in an axialdirection from the engine compressor or compressors. Alternatively, thesystems may be employed to supply fuel for reheating purposes, that iscombustion which is effected in the exhaust of the engine.

We claim:

1. A fuel control system for supplying fuel to primary and main burnersin a gas turbine engine, including a pump, fuelpassage-defining meansproviding communication between the pump and the burners respectively, amanually operable valve having portions simultaneously controlling flowto the primary and main burners respectively, a servo-operated throttlevalve in the fuel-passage-defining means for controlling flow to theburners, a device to which higher and lower air pressures obtained fromthe engine are applied, a pressure-responsive means in said device towhich said pressures are applied, a valve in said device controlled bythe pressure responsive means, said valve controlling the fuel flow tothe primary burners, a second valve in said device arranged forcontrolling the pressure of fuel to the servo-operated throttle valvefor controlling the fuel flow therethrough, means responsive to thepressure of fuel flowing to the primary burners, said last named meansbeing arranged to actuate said second valve, and a device in thepassage-defining means to the main burners arranged for controlling thefuel flow to the main burners at a rate proportional to that to theprimary burners, said last named device comprising a valve arranged forcreating a pressure drop in said passage-defining means, and said deviceand valve controlled by the higher and lower air pressures forcontrolling flow of fuel to the primary burners being arranged forcreating equal pressure drops.

2, A fuel control system for supplying fuel to primary and main burnersin a gas turbine engine, comprising a pump, a turbine for driving thepump, a passage in which the turbine is positioned, said passagecommunicating with the engine for receiving a supply of air therefromfor driving the turbine, a manual control valve in the passage betweenthe engine and the turbine, fuel passage means providing communicationbetween the pump and the burners in the engine respectively, a manuallyoperable valve having portions simultaneously controlling flow to theprimary and main burners respectively, a servo-operated throttle valvein the fuel passage means controlling flow to the burners, a device towhich higher and lower air pressures obtained from the engine areapplied, a pressure-responsive means in said device to which saidpressures are applied, a valve in said device controlled by saidpressure-responsive means for controlling the fuel flow to the primaryburners, a second valve in said device for controlling the pressure offuel to the servo-operated throttle valve for controlling the fuel flowtherethrough, means responsive to the pressure of fuel flowing to theprimary burners, said last name means being arranged for actuating saidsecond valve, and a device in the passage to the main burners arrangedfor controlling the fuel flow to the main burners at a rate proportionalto that to the primary burners.

3. A fuel control system for use with a gas turbine engine of the typehaving a fan driven by the engine and a duct through which air deliveredby the fan can flow, primary and main burners in the duct, said systemincluding a pump, fuel passage defining means providing communicationbetween the pump and the burners in the engine respectively, a manuallyopera' ble valve having portions simultaneously controlling flow to theprimary and main burners respectively, a servo-operated throttle valvein the fuel-passage-defining means for controlling flow to the burners,a device to which higher and lower air pressures obtained from theengine are applied, a pressure-responsive means in said device to whichsaid pressures are applied, a valve in said device controlled by saidpressure-responsive means controlling the fuel flow to the primaryburners, a second valve in said device for controlling the pressure offuel to the servo-operated throttle valve for controlling fuel flowtherethrough, means responsive to the pressure of fuel flowing to theprimary burners arranged for actuating said second valve, and a devicein the fuel passage defining means for controlling the fuel flow to themain burners at a rate proportional to that to the primary burners.

41. A fuel control system for use with a gas turbine engine of the typehaving a fan driven by the engine and a duct through which air deliveredby the fan can flow, primary and main burners in the duct, said systemincluding a pump, fuel-passagedefining means providing communicationbetween the pump and the burners in the engine respectively, a manuallyopera ble valve having portions simultaneously controlling flow to theprimary and main burners respectively, a servo-operated throttle valvein the fuel-passage-defining means for controlling flow to the burners,a device to which higher and lower air pressures obtained from theengine are applied, a pressure-responsive means in said device to whichsaid pressures are applied, a valve in said device controlled by saidpressure-responsive means controlling the fuel flow to the primaryburners, a second valve in said device for controlling the pressure offuel to the servo-operated throttle valve for controlling fuel flowtherethrough, means responsive to the pressure of the fuel flowing tothe primary burners arranged for actuating said second valve, and adevice in the fuel passage defining means for controlling the fuel flowto the main burners at a rate proportional to that to the primaryburners, the valve for controlling the fuel flow to the primary burnersinwas

1. A fuel control system for supplying fuel to primary and main burnersin a gas turbine engine, including a pump, fuel-passagedefining meansproviding communication between the pump and the burners respectively, amanually operable valve having portions simultaneously controlling flowto the primary and main burners respectively, a servo-operated throttlevalve in the fuelpassage-defining means for controlling flow to theburners, a device to which higher and lower air pressures obtained fromthe engine are applied, a pressure-responsive means in said device towhich said pressures are applied, a valve in said device controlled bythe pressure responsive means, said valve controlling the fuel flow tothe primary burners, a second valve in said device arranged forcontrolling the pressure of fuel to the servo-operated throttle valvefor controlling the fuel flow therethrough, means responsive to thepressure of fuel flowing to the primary burners, said last named meansbeing arranged to actuate said second valve, and a device in thepassage-defining means to the main burners arranged for controlling thefuel flow to the main burners at a rate proportional to that to theprimary burners, said last named device comprising a valve arranged forcreating a pressure drop in said passage-defining means, and said deviceand valve controlled by the higher and lower air pressures forcontrolling flow of fuel to the primary burners being arranged forcreating equal pressure drops.
 2. A fuel control system for supplyingfuel to primary and main burners in a gas turbine engine, comprising apump, a turbine for driving the pump, a passage in which the turbine ispositioned, said passage communicating with the engine for receiving asupply of air therefrom for driving the turbine, a manual control valvein the passage between the engine and the turbine, fuel passage meansproviding communication between the pump and the burners in the enginerespectively, a manually operable valve having portions simultaneouslycontrolling flow to the primary and main burners respectively, aservo-operated throttle valve in the fuel passage means controlling flowto the burners, a device to which higher and lower air pressuresobtained from the engine are applied, a pressure-responsive means insaid device to which said pressures are applied, a valve in said devicecontrolled by said pressure-responsive means for controlling the fuelflow to the primary burners, a second valve in said device forcontrolling the pressure of fuel to the servo-operated throttle valvefor controlling the fuel flow therethrough, means responsive to thepressure of fuel flowing to the primary burners, said last name meansbeing arranged for actuating said second valve, and a device in thepassage to the main burners arranged for controlling the fuel flow tothe main burners at a rate proportional to that to the primary burners.3. A fuel control system for use with a gas turbine engine of the typehaving a fan driven by the engine and a duct through which air deliveredby the fan can flow, primary and main burners in the duct, said systemincluding a pUmp, fuel passage defining means providing communicationbetween the pump and the burners in the engine respectively, a manuallyoperable valve having portions simultaneously controlling flow to theprimary and main burners respectively, a servo-operated throttle valvein the fuel-passage-defining means for controlling flow to the burners,a device to which higher and lower air pressures obtained from theengine are applied, a pressure-responsive means in said device to whichsaid pressures are applied, a valve in said device controlled by saidpressure-responsive means controlling the fuel flow to the primaryburners, a second valve in said device for controlling the pressure offuel to the servo-operated throttle valve for controlling fuel flowtherethrough, means responsive to the pressure of fuel flowing to theprimary burners arranged for actuating said second valve, and a devicein the fuel passage defining means for controlling the fuel flow to themain burners at a rate proportional to that to the primary burners.
 4. Afuel control system for use with a gas turbine engine of the type havinga fan driven by the engine and a duct through which air delivered by thefan can flow, primary and main burners in the duct, said systemincluding a pump, fuel-passage-defining means providing communicationbetween the pump and the burners in the engine respectively, a manuallyoperable valve having portions simultaneously controlling flow to theprimary and main burners respectively, a servo-operated throttle valvein the fuel-passage-defining means for controlling flow to the burners,a device to which higher and lower air pressures obtained from theengine are applied, a pressure-responsive means in said device to whichsaid pressures are applied, a valve in said device controlled by saidpressure-responsive means controlling the fuel flow to the primaryburners, a second valve in said device for controlling the pressure offuel to the servo-operated throttle valve for controlling fuel flowtherethrough, means responsive to the pressure of the fuel flowing tothe primary burners arranged for actuating said second valve, and adevice in the fuel passage defining means for controlling the fuel flowto the main burners at a rate proportional to that to the primaryburners, the valve for controlling the fuel flow to the primary burnersincluding a piston, the position of which is determined by the pressureof fuel flowing through the valve on one side and by the pressure offuel controlled by a further valve on the other side, and said furthervalve being controlled in turn by the pressure-responsive means to whichthe air pressures are applied.